Department of Environmental Science, The University of Arizona, Tucson, AZ 85721, USA.
Department of Environmental Science, The University of Arizona, Tucson, AZ 85721, USA; Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Sci Total Environ. 2022 Jan 15;804:150045. doi: 10.1016/j.scitotenv.2021.150045. Epub 2021 Sep 1.
Understanding the effects of elevated temperatures on soil organic matter (SOM) decomposition pathways in northern peatlands is central to predicting their fate under future warming. Peatlands role as carbon (C) sink is dependent on both anoxic conditions and low temperatures that limit SOM decomposition. Previous studies have shown that elevated temperatures due to climate change can disrupt peatland's C balance by enhancing SOM decomposition and increasing CO emissions. However, little is known about how SOM decomposition pathways change at higher temperatures. Here, we used an integrated research approach to investigate the mechanisms behind enhanced CO emissions and SOM decomposition under elevated temperatures of surface peat soil collected from a raised and Sphagnum dominated mid-continental bog (S1 bog) peatland at the Marcel Experimental Forest in Minnesota, USA, incubated under oxic conditions at three different temperatures (4, 21, and 35 °C). Our results indicated that elevated temperatures could destabilize peatland's C pool via a combination of abiotic and biotic processes. In particular, temperature-driven changes in redox conditions can lead to abiotic destabilization of Fe-organic matter (phenol) complexes, previously an underestimated decomposition pathway in peatlands, leading to increased CO production and accumulation of polyphenol-like compounds that could further inhibit extracellular enzyme activities and/or fuel the microbial communities with labile compounds. Further, increased temperatures can alter strategies of microbial communities for nutrient acquisition via changes in the activities of extracellular enzymes by priming SOM decomposition, leading to enhanced CO emission from peatlands. Therefore, coupled biotic and abiotic processes need to be incorporated into process-based climate models to predict the fate of SOM under elevated temperatures and to project the likely impacts of environmental change on northern peatlands and CO emissions.
了解高温对北方泥炭地土壤有机质 (SOM) 分解途径的影响对于预测未来变暖条件下它们的命运至关重要。泥炭地作为碳 (C) 汇的作用取决于缺氧条件和限制 SOM 分解的低温。先前的研究表明，由于气候变化导致的气温升高会通过增强 SOM 分解和增加 CO 排放来破坏泥炭地的 C 平衡。然而，对于 SOM 分解途径在更高温度下如何变化知之甚少。在这里，我们使用综合研究方法来研究美国明尼苏达州马塞尔实验林升高和水藓占主导地位的中大陆沼泽 (S1 沼泽) 泥炭地表层泥炭土壤在升高温度下增强 CO 排放和 SOM 分解的机制，这些土壤在有氧条件下在三个不同温度（4、21 和 35°C）下进行培养。我们的研究结果表明，升高的温度可以通过非生物和生物过程的结合来破坏泥炭地的 C 库。特别是，氧化还原条件的温度变化会导致先前在泥炭地中被低估的分解途径——Fe-有机质（酚）复合物的非生物失稳，从而导致 CO 产量增加和多酚类化合物的积累，这可能进一步抑制胞外酶活性和/或为微生物群落提供易降解化合物作为燃料。此外，升高的温度可以通过改变胞外酶的活性来改变微生物群落获取养分的策略，从而促进泥炭地的 CO 排放。因此，需要将生物和非生物过程结合到基于过程的气候模型中，以预测 SOM 在升高温度下的命运，并预测环境变化对北方泥炭地和 CO 排放的可能影响。
